Swine flu continued its global march as South Korea confirmed its first case and Hong Kong and China scrambled to track down anybody who had been in contact with an infected Mexican man.

But amid the spread of the virus, health authorities said the world appeared better prepared to fight an epidemic than a few years ago, and vowed that a vaccine was only months away.

Hong Kong was placed on its highest health alert after the 25-year-old Mexican tested positive for the A(H1N1) virus on Friday, the first confirmed case of swine flu in Asia.

Officials in Hong Kong, China and Taiwan were desperately trying to reach anyone who may have come into contact with the man during his journey from Mexico, via Shanghai.

As some pharmacies in sold out of protective masks, more than 300 guests and staff at a hotel where the Mexican stayed were put in isolation for seven days and authorities were trying to locate fellow air passengers.

China said it was to put all passengers on the flight from Mexico to Shanghai under quarantine and that flights from Mexico to the city were being suspended.